From 7b6e641ce4267249c3948e732012b89d15d999ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Josip=20Ti=C5=A1ljar=20Matau=C5=A1i=C4=87?=
 <josip.tismat@gmail.com>
Date: Thu, 21 May 2026 17:46:52 +0200
Subject: [PATCH] [feat] Insertion of Gopher specific content and ommition of
 web-only content

---
 README.md | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 main.go   | 34 +++++++++++++++++++++---
 2 files changed, 107 insertions(+), 4 deletions(-)
 create mode 100644 README.md

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..f710751
--- /dev/null
+++ b/README.md
@@ -0,0 +1,77 @@
+
+### Compiling
+
+This program compiles like any other ordinary Go project, simply **run** `go build .` in the project directory.
+
+### Usage
+```shell
+gemtext2gophermap input.gmi output_gophermap [max line length (default 70)] [preprocessor insertion map file]
+```
+
+## Example
+
+### Input Gemtext
+_input.gmi_
+````gemtext
+Everything until the first <!--break--> in the map file will be put in place of the insert-gopher tag.
+
+```html
+<!--insert-gopher-->
+```
+
+The following <script> tag will be removed because it is between to web-only tags.
+
+```html
+<!--web-only-->
+```
+
+```html
+<script>
+console.log("joj")
+</script>
+```
+
+```html
+<!--web-only-->
+```
+
+> Here, the contents after the first break in the map file will be put
+
+```html
+<!--insert-gopher-->
+```
+````
+
+### A map file
+_map.txt_
+```gophermap
+<?php
+echo "i" . date(DATE_RFC2822) . "\t/FAKE\tNULL\t0";
+?>
+<!--break-->
+iIf your Gopher server supports running PHP it should have printed the current date.	/FAKE	NULL	0
+```
+
+### Command
+```shell
+gemtext2gophermap input.gmi - 70 map.txt
+```
+If `-` is passed instead of `input/output` file name `stdin/stdout` will be used. Reading the **map file from stdin** is **not supported**.
+
+### Output
+```gophermap
+iEverything until the first <!--break--> in the map file will be put in /FAKE   NULL    0
+iplace of the insert-gopher tag.        /FAKE   NULL    0
+
+<?php
+echo "i" . date(DATE_RFC2822) . "\t/FAKE\tNULL\t0";
+?>
+
+iThe following <script> tag will be removed because it is between to    /FAKE   NULL    0
+iweb-only tags. /FAKE   NULL    0
+
+i> Here, the contents after the first break in the map file will be put /FAKE   NULL    0
+
+
+iIf your Gopher server supports running PHP it should have printed the current date.    /FAKE   NULL    0
+```
diff --git a/main.go b/main.go
index ca48b77..e6beed4 100644
--- a/main.go
+++ b/main.go
@@ -10,15 +10,18 @@ import(
 )
 
 type State struct {
-	out io.Writer	
+	out io.Writer
 	maxLineLength int
+	insertionMap []string
+	insertionIndex int
 	isInCodeBlock bool
 	wasPreviousLink bool
+	isWebOnly bool
 }
 
 func main() {
 	if len(os.Args) < 3 {
-		fmt.Printf("Usage: %s input.gmi output_gophermap [max line length (default 69)]\n", os.Args[0])
+		fmt.Printf("Usage: %s input.gmi output_gophermap [max line length (default 70)] [preprocessor insertion map file]\n", os.Args[0])
 		return
 	}
 
@@ -52,7 +55,17 @@ func main() {
 		outputWriter = os.Stdout
 	}
 
-	s := State{outputWriter, 69, false, false}
+	preprocessorMap := []string{}
+	if len(os.Args) >= 5 {
+		data, err := os.ReadFile(os.Args[4])
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		preprocessorMap = strings.Split(string(data), "<!--break-->")
+	}
+
+	s := State{outputWriter, 70, preprocessorMap, 0, false, false, false}
 	if len(os.Args) >= 4 {
 		maxLineLength, err := strconv.Atoi(os.Args[3])
 		if err != nil {
@@ -72,6 +85,17 @@ var gopherTypeCharParams = GopherTypeCharParams{
 }
 
 func (s *State) handleElement(e p.Element) {
+	if strings.HasPrefix(e.Text(), "<!--web-only-->") {
+		s.isWebOnly = !s.isWebOnly
+		return
+	}
+	if s.isWebOnly { return }
+	if strings.HasPrefix(e.Text(), "<!--insert-gopher-->") {
+		s.out.Write([]byte(s.insertionMap[s.insertionIndex]))
+		s.insertionIndex += 1
+		return
+	}
+
 	switch (e.Type()) {
 		case p.ElementTypes.Text():
 			if e.Text() == "" { return }
@@ -110,5 +134,7 @@ func (s *State) handleElement(e p.Element) {
 			s.isInCodeBlock = !s.isInCodeBlock
 			s.wasPreviousLink = false
 	}
-	s.out.Write([]byte("\n"))
+	if e.Text() != "" {
+		s.out.Write([]byte("\n"))
+	}
 }